Ink jet printhead nozzle arrangement with actuated nozzle chamber closure

1. A nozzle arrangement for an ink jet printhead chip, the nozzle arrangement comprising

a wafer substrate having a front surface, a rear surface and a nozzle chamber extending through the wafer substrate to define an inlet at the rear surface of the wafer substrate and an outlet at the front surface of the wafer substrate, the nozzle chamber being in fluid communication with an ink supply at the rear surface of the wafer substrate;

a closure member positioned on the rear surface of the substrate and being displaceable between open and closed positions to control a flow of ink through the wafer substrate; and

an actuator operatively engaged with the closure member to displace the closure member between the open and closed positions, when activated; wherein,

the chamber, the outlet and the actuator are dimensioned with respect to the ink properties such that the ink is retained within the chamber when the closure member is in the closed position by the ink surface across the outlet.

2. A nozzle arrangement as claimed in claim 1 , in which the rear surface is substantially planar and the closure member is constrained to move in a plane substantially parallel to the rear surface.

3. A nozzle arrangement as claimed in claim 2 , in which the closure member is constrained to move between the open and closed positions along a linear path.

4. A nozzle arrangement as claimed in claim 1 , wherein the actuator engages the closure member via a gear train.

5. A nozzle arrangement as claimed in claim 4 , wherein the gear train includes at least one rotating gear wheel and a linear gear positioned on the closure member.

6. A nozzle arrangement as claimed in claim 1 , in which a drive circuitry layer is positioned on the rear surface of the wafer substrate and is electrically connected to the actuator, so tat the actuator can be activated by a signal received from the drive circuitry layer.